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A New View of Cosmic X-rays

TOKYO--After a failed attempt 5 years ago, Japan successfully launched the ASTRO-E2 x-ray satellite yesterday. The mission, a joint effort of NASA and the Japan Aerospace Exploration Agency (JAXA), should give scientists further clues to the nature of black holes and dark matter.

ASTRO-E2 carries the same six instruments as the ill-fated ASTRO-E, which was incinerated after launch (ScienceNOW, 10 February, 2000). But their performance has been improved. And recent findings from NASA's Chandra X-ray Observatory and the European XMM-Newton Observatory have allowed scientists to hone their list of observational targets.

ASTRO-E2's crown jewel is the X-ray Spectrometer (XRS). XRS "allows investigations that have never been possible before," says Andrew Fabian, an astrophysicist at University of Cambridge, the United Kingdom, a science advisor to the mission. Developed by JAXA's Institute for Space and Astronautical Science (ISAS) and NASA, XRS measures the energy of individual xray photons. The original XRS had higher spectral resolution, or a greater ability to distinguish energy levels, than any other x-ray instrument in space. By eliminating some sources of noise, scientists doubled that resolution. And improved cryogenics add a half year or more to the 2-year life of the instrument.

These improved capabilities will be put to good use. Richard Kelley, NASA's principal investigator for the XRS, explains that Chandra has seen evidence of blobs of material in the accretion disks surrounding certain black holes. ASTRO-E2 should be able to determine if these blobs are real and then to use them "as probes to tell whether the general picture of matter spiraling (into a black hole) makes sense," he says. The XRS should also be able to confirm previous glimpses of the tell-tale distortion of x-ray emissions expected when iron elements are subjected to a black hole's intense gravitational pull, as predicted by Einstein's general relativity theory. XRS will also be looking at clusters of galaxies for clues to the role of dark matter in their evolution and dynamics.

The satellite was given a new name, "Suzaku," Japanese for "red phoenix", after its launch. But mission scientists caution there are still hurdles to clear. "We can't be completely at ease yet," says ISAS astrophysicist Noriko Yamasaki, who noted that it will take a few weeks to verify that the satellite and the instruments are operating properly. If all goes well, scientific observations will start early next month.